Electrochemical CO2 reduction reaction (CO2RR), when powered with intermittent but renewable energies,
holds
an attractive potential to close the anthropogenic carbon cycle through
efficiently converting the exorbitantly discharged CO2 to
value-added fuels and/or chemicals and consequently reduce the greenhouse
gas emission. Through systematically integrating the density functional
theory calculations, the modeling statistics of various proportions
of CO2RR-preferred electroactive sites, and the theoretical
work function results, it is found that the crystallographically unambiguous
Ag nanoclusters (NCs) hold a high possibility to enable an outstanding
CO2RR performance, particularly at an optimal size of around
2 nm. Motivated by this, homogeneously well-distributed ultrasmall
Ag NCs with an average size of ∼2 nm (2 nm Ag NCs) were thus
synthesized to electrochemically promote CO2RR, and the
results demonstrate that the 2 nm Ag NCs are able to achieve a significantly
larger CO partial current density [j
(CO)], an impressively higher CO Faraday efficiency of over 93.8%, and
a lower onset overpotential (η) of 146 mV as well as a remarkably
higher energy efficiency of 62.8% and a superior stability of 45 h
as compared to Ag nanoparticles (Ag NPs) and bulk Ag. Both theoretical
computations and experimental results clearly and persuasively demonstrate
an impressive promotion effect of the crystallographically explicit
atomic structure for electrochemically reducing CO2 to
CO, which exemplifies a novel design approach to more benchmark metal-based
platforms for advancing the practically large-scale CO2RR application.
Red mud (RM) is a solid waste generated during the process of alumina production. RM has already posed a serious environmental threat with the development of the alumina refining industry. The comprehensive utilization of RM has attracted much attention due to its large-scale generation and harmful nature. This paper introduces the characteristics and state of RM and summarizes the relevant research on the comprehensive utilization of RM. The results show that comprehensive utilization of RM is mainly focused on the preparation of building materials, the extraction of valuable metals, catalyst synthesis and environmental protection. Besides, the article discusses the existing problems while utilizing RM. Prospects and suggestions for different utilization methods of RM are proposed.
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